Colorant composition, ink, printing process

ABSTRACT

A composition comprising a compound of Formula (1) or a salt thereof and compound of Formula (2) or a salt thereof: 
                         
wherein:
     A is or comprises an aryl or heteroaryl group;   Q 1  and Q 2  each independently is an optionally substituted phenylene group;   R 1 , R 2 , R a  and R b  each independently is H, optionally substituted alkyl, optionally substituted aryl or optionally substituted arylalkyl;   each W 1 , W 2 , W 3  and W 4  independently is a —CO 2 H, —SO 3 H, —PO 3 H 2  group or an alkyl substituted with one or more groups selected from —CO 2 H, —SO 3 H, —PO 3 H 2 ;   each S 1 , S 2 , S 3  and S 4  independently is a substituent other than those defined for W 1 , W 2 , W 3  and W 4 ;   a and d each independently is from 1 to 5;   b and c each independently is from 0 to 4;   (a+b) has a value of from 1 to 5;   (c+d) has a value of from 1 to 5;   e and h each independently is from 1 to 7;   f and g each independently is from 0 to 6;   (e+f) has a value of from 1 to 7; and   (g+h) has a value of from 1 to 7.

This is a 371 filing based on PCT/GB2008/001967 filed Jun. 10, 2008 andclaiming priority from Great Britain Application No. 0711963.9, filedJun. 21, 2007.

This invention relates to colorant compositions (especially, but notexclusively yellow colorant compositions), to inks containing saidcolorant compositions and to the use of said inks in ink jet printing(“IJP”).

Ink jet printing is a non-impact printing technique in which droplets ofink are ejected through fine nozzles onto a substrate without bringingthe nozzle into contact with the substrate.

There are many demanding performance requirements for colorants and inksused in IJP. For example, they desirably provide sharp, non-featheredimages having good water-fastness, light-fastness, ozone-fastness andoptical density. The inks are often required to dry quickly when appliedto a substrate to prevent smudging, but they should not form a crustover the tip of an ink jet nozzle because this will tend to reduce printquality and in extreme cases may prevent the printer from printing. Theinks are preferably also stable to storage over time without decomposingor forming a precipitate which could block the fine nozzle.

U.S. Pat. No. 6,488,752 discloses several azo containing compounds foruse in ink jet printing.

For colorants used in ink jet printing inks it is often difficult tosimultaneously achieve good chroma, hue, light-fastness andozone-fastness. Also, it is desirable to provide good performanceproperties using economically efficient technologies. A furtherdesirable property is that prints should not significantly change hue orcolour when stored, exposed to light or when exposed to ozone. Forexample, a yellow print should preferably stay yellow in colour whenexposed to sunlight rather than change to a more red or blue shade.

The present invention aims to address, at least in part, one or more ofthe abovementioned desirable technical goals.

According to a first aspect of the present invention there is provided acomposition comprising a compound of Formula (1) or a salt thereof andcompound of Formula (2) or a salt thereof:

wherein:

-   A is or comprises an aryl or heteroaryl group;-   Q¹ and Q² each independently is an optionally substituted phenylene    group;-   R¹, R², R^(a) and R^(b) each independently is H, optionally    substituted alkyl, optionally substituted aryl or optionally    substituted arylalkyl;-   each W¹, W², W³ and W⁴ independently is a —CO₂H, —SO₃H, —PO₃H₂ group    or an alkyl substituted with one or more groups selected from —CO₂H,    —SO₃H, —PO₃H₂;-   each S¹, S², S³ and S⁴ independently is a substituent other than    those defined for W¹, W², W³ and W⁴;-   a and d each independently is from 1 to 5;-   b and c each independently is from 0 to 4;-   (a+b) has a value of from 1 to 5;-   (c+d) has a value of from 1 to 5;-   e and h each independently is from 1 to 7;-   f and g each independently is from 0 to 6;-   (e+f) has a value of from 1 to 7; and-   (g+h) has a value of from 1 to 7.

In Formula (1), b and c are preferably each independently 0, 1 or 2,more preferably 0 or 1.

In Formula (1) a and d are preferably each independently 1, 2, or 3,more preferably 1 or 2.

Preferably (a+b) has a value of 1, 2 or 3, more preferably 1 or 2.Preferably (c+d) has a value of 1, 2 or 3, more preferably 2 or 3.

The compound of Formula (1) or a salt thereof is preferably a mono azocompound (i.e. containing only one azo (—N═N—) group).

In one embodiment A is an aryl group, more preferably a naphthyl orphenyl group and especially a phenyl group.

In another embodiment A is an indanyl group, more preferably A is anindanyl group of the Formula (1a):

wherein the asterisk represents the point of attachment to the azo groupin the compound of Formula (1).

Preferably each W¹ and each W² independently is —CO₂H, —SO₃H, —PO₃H₂ orC₁₋₁₀alkyl (more preferably C₁₋₆-alkyl) substituted by one, two or three(more preferably one) groups selected from —CO₂H, —SO₃H, and —PO₃H₂.

More preferably each W¹ and each W² independently is —CO₂H, —SO₃H orC₁₋₆-alkyl substituted by —CO₂H or —SO₃H.

It is especially preferred that each W¹ independently is —CO₂H or —SO₃H.

It is especially preferred that each W² is —CO₂H.

Preferably at least one W¹ is attached in an ortho position relative tothe azo group (—N═N—).

Preferably S¹ and S² are each independently optionally substituted aryl,optionally substituted aralkyl, halogen (especially F and Cl), nitro,cyano, —CF₃, —OR³, —NR⁴R⁵, —SR⁶, —C(O)R⁷, —C(O)OR⁸, —SO₂R⁹, —SOR¹⁰,alkyl optionally substituted by a group other than —SO₃H, —CO₂H or—PO₃H₂ or a group of Formula (1b):

wherein:

-   R³ and R⁶ each independently is H, optionally substituted alkyl or    optionally substituted aryl;-   R⁴ and R⁵ each independently is H, optionally substituted alkyl,    optionally substituted aryl, —CO(C₁₋₆-alkyl), —CONH₂, or R⁴ and R⁵    together with the nitrogen to which they are attached form a 5- or    6-membered ring;-   R⁷, R⁸, R⁹ and R¹⁰ each independently is optionally substituted    alkyl or optionally substituted aryl;    the group of Formula (1b) is:

wherein

-   L¹ and L² each independently is —OR¹¹, —SR¹² or —NR¹³R¹⁴;-   R¹¹ and R¹² each independently is H, optionally substituted aryl or    optionally substituted alkyl; and-   R¹³ and R¹⁴ each independently is H, optionally substituted aryl,    optionally substituted alkyl, —CO(C₁₋₆-alkyl), —CONH₂ or R¹³ and R¹⁴    together with the nitrogen to which they are attached form an    optionally substituted morpholine or piperazine ring;-   V is —N(R¹⁵)— or —S—;-   R¹⁵ is H, optionally substituted alkyl or optionally substituted    aryl; and    the asterisk (*) represents the point of attachment to the group    represented by A.

In a preferred embodiment S¹ and S² are each independently optionallysubstituted aryl, optionally substituted aralkyl, halogen (especially Fand Cl), nitro, cyano, —CF₃, —OR³, —NR⁴R⁵, —SR⁶, —C(O)R⁷, —C(O)OR⁸,—SO₂R⁹, —SOR¹⁰ or alkyl optionally substituted by a group other than—SO₃H, —CO₂H or —PO₃H₂; wherein R³, R⁴, R⁵, R⁶ R⁷, R⁸, R⁹ and R¹⁰ are ashereinbefore defined.

Preferably R⁷, R⁸, R⁹ and R¹⁰ are each independently optionallysubstituted alkyl.

When any of S¹ and S² is optionally substituted alkyl it is preferablyoptionally substituted C₁₋₁₀-alkyl, more preferably C₁₋₆-alkyloptionally substituted by —OH, nitro, cyano, halogen (especially F orCl), amino, —NH(C₁₋₄-hydroxyalkyl) or —NH(C₁₋₄-alkyl).

When any one of R³, R⁴, R⁵, R⁶, R⁷, R⁸, R⁹, R¹⁰, R¹¹, R¹², R¹³, R¹⁴ andR¹⁵ is optionally substituted alkyl it is preferably optionallysubstituted C₁₋₁₀-alkyl, more preferably optionally substitutedC₁₋₆-alkyl. Preferred optional substituents are —OH, nitro, cyano, aminoand halogen (preferably F or Cl), more especially Cl and —OH.

When one any of R³, R⁴, R⁵, R⁶, R⁷, R⁸, R⁹, R¹⁰, R¹¹, R¹², R¹³, R¹⁴ andR¹⁵ is optionally substituted aryl it is preferably optionallysubstituted phenyl or optionally substituted naphthyl, especiallyoptionally substituted phenyl. Preferred optional substituents areC₁₋₄-alkoxy, (C₁₋₄-hydroxyalkoxy)-C₁₋₄-alkoxy-, —OH, —CO₂H, —SO₃H, —CF₃,amino, —NH(C₁₋₄-alkyl), —NH(C₁₋₄-hydroxyalkyl), —NH(—CO(C₁₋₄-alkyl)),halogen (especially F or Cl), nitro, —CO(C₁₋₄-alkyl), —SO₂(C₁₋₄alkyl)and C₁₋₄-alkyl optionally substituted by —OH, —CO₂H and —SO₃H.

When R⁴ and R⁵ together with the nitrogen to which they are attachedform a 5 or 6 membered ring, the ring is preferably optionallysubstituted morpholine or optionally substituted piperazine.

Preferred optional substituents on the rings which may be formed by R⁴and R⁵, and R¹³ and R¹⁴, together with the nitrogen to which they areattached are selected from —OH, —CO₂H, —SO₃H, O₁₋₄-alkoxy and C₁₋₄-alkyloptionally substituted by —OH, —CO₂H or —SO₃H.

R⁷, R⁸, R⁹ and R¹⁰ are preferably each independently C₁₋₄-alkyl, morepreferably methyl or ethyl.

When any one of S¹ and S² is aralkyl it is preferably optionallysubstituted phenyl-(alkylene)- or optionally substitutednaphthyl-(alkylene)-, more preferably optionally substitutedphenyl-(C₁₋₆-alkylene)- or optionally substitutednaphthyl-(C₁₋₆-alkylene)-. Preferred optional substituents on thearalkyl groups are those listed above for the aryl groups, morepreferably C₁₋₄-alkyl, C₁₋₄-alkoxy, —SO₃H, —CO₂H, amino, nitro, F or Cl.

Preferably each S¹ and each S² is has no —CO₂H, —SO₃H and —PO₃H₂ groups.

Preferably each S¹ and S² independently is C₁₋₄-alkyl or C₁₋₄ alkoxy.

Preferably, c is from 0 to 3, more preferably c is 0.

Preferably, b is from 0 to 3, more preferably b is 0.

Preferably R¹ is H, optionally substituted C₁₋₁₀-alkyl, optionallysubstituted phenyl or optionally substituted phenyl-(C₁₋₆-alkylene)-,more preferably H, phenyl, C₁₋₆-alkyl optionally substituted by —OH,—SO₃H or —CO₂H, especially H or C₁₋₄-alkyl, more especially H.

Preferably R² is optionally substituted C₁₋₁₀-alkyl, optionallysubstituted phenyl, more preferably phenyl, or C₁₋₆-alkyl optionallysubstituted by —OH, —CO₂H or —SO₃H, especially C₁₋₄-alkyl, moreespecially methyl or ethyl. Most preferably R² is methyl.

In a preferred compound of Formula (1) or salt thereof:

-   A is as hereinbefore defined;-   each W¹ and each W² independently is —CO₂H, —SO₃H or a C₁₋₆ alkyl    substituted by —CO₂H or —SO₃H;-   each S¹ and S² independently is C₁₋₆ alkyl, phenyl, nitro, halo    (especially F and Cl), cyano, —CF₃, —NH₂, C₁₋₆ alkoxy, —SC₁₋₆ alkyl,    —C₁₋₆ alkyl substituted by —OH or —NHC(O)C₁₋₆ alkyl;-   R¹ is H or C₁₋₆-alkyl optionally substituted by —OH, —SO₃H or —CO₂H;-   R² is C₁₋₄ alkyl;-   a and d each independently is 1 or 2;-   b and c each independently is 0, 1 or 2.

Preferably, W² is —CO₂H.

Preferably, each W¹ independently is —CO₂H or SO₃H.

Preferably, R¹ is H or C₁₋₄ alkyl, more preferably H.

Preferably, R² is methyl or ethyl, more preferably methyl.

It is especially preferred that a is 1 and W² is —CO₂H which is attachedto the pryrridinium ring in the 3-position.

Preferably, A is phenyl or indanyl

A particularly preferred compound of Formula (1) or a salt thereof is ofFormula (3) or a salt thereof:

The compound of Formula (3) has a particularly bright yellow colour andhigh chroma, it also exhibits especially good light-fastness.

In one embodiment the compound of Formula (1) or a salt thereof is ofFormula (1c) or a salt thereof:

wherein:

W¹, W², S¹, S², R¹ and R² a, b, c and d are as hereinbefore defined.

Preferably, d is from 1 to 3, c is from 0 to 3 and (c+d) is from 1 to 3.In this embodiment all the groups represented by each W¹ and each S¹ arepreferably attached to the benzyl ring present in the compound ofFormula (1c).

Preferably each S¹ independently is C₁₋₆-alkyl or C₁₋₆-alkoxy each ofwhich is optionally substituted by —OH.

In Formula (1c) c is preferably 0. Preferably d is 1 or 2. It isespecially preferred in Formula (1c) that c is 0, a is 1 or 2 and atleast one W¹ is ortho relative to the azo group in Formula (1c).

The compound of Formula (1) or a salt thereof may be prepared by thesynthetic methods as described in U.S. Pat. No. 6,488,752 at column 5.

The compound of Formula (3) or a salt thereof may be prepared by themethod described in U.S. Pat. No. 6,488,752, Example 1, beginning atcolumn 10.

The compound of Formula (2) or a salt thereof preferably contains onlytwo azo groups.

Preferably, one or both of the naphthyl groups present in the compoundof Formula (2) or a salt thereof are attached to the relevant azo grouppresent in the compound of Formula (2) in the 2-napthyl position.

Accordingly, a preferred compound of Formula (2) or a salt thereof is ofFormula (2a) or a salt thereof:

wherein Q¹, Q², W³, W⁴, S³, S⁴, R^(a), R^(b) e, f, g and h are ashereinbefore defined.

Q¹ is preferably a phenylene group which is para connected to the —N═N—group and the —NR^(a)— group present in the compound of Formula (2).

Similarly, Q² is preferably a phenylene group which is para connected tothe —N═N— group and the —NR^(b)— group present in the compound ofFormula (2).

Q¹ and Q² may optionally be substituted with from 1 to 4 groups (morepreferably 1 or 2 groups) each independently selected from any of thoseas defined above for W¹ and S¹.

Preferably, Q¹ and Q² do not contain any —CO₂H, —SO₃H and —PO₃H₂ groups.

Preferably, Q¹ and Q² are each independently substituted with 1 or 2groups selected from O₁₋₆ alkyl, C₁₋₆ alkoxy, —C(O)OC₁₋₆ alkyl and—C(O)NHC₁₋₆ alkyl groups.

Preferably, Q¹ and Q² are substituted with at least one C₁₋₆ alkyl, morepreferably at least one methyl group. Preferably, a C₁₋₆ alkyl group ispresent in Q¹ and Q² in a position which is ortho relative to therelevant azo (—N═N—) group in the compound of Formula (2).

Preferably, Q¹ is of the Formula (2b):

wherein

-   R¹⁶ is H or methyl;    the asterisk (*) symbol represents the point of attachment to the    azo group and the hash (#) symbol represents the point of attachment    to the —NR^(a)— group present in the compound of Formula (2).

Similarly, Q² is preferably of Formula (2c):

wherein

-   R¹⁷ is H or methyl;    the asterisk (*) symbol represents the point of attachment to the    azo group and the hash (#) symbol represents the point of attachment    to the —NR^(b)— group present in the compound of Formula (2).

R^(a) and R^(b) may each independently be any of the groups ashereinbefore defined for R¹.

Preferably, R^(a) and R^(b) are each independently H or C₁₋₆ alkyloptionally substituted with from one to three (especially just one)—CO₂H, —OH or SO₃H groups.

Preferably, R^(a) and R^(b) are H.

Preferably, h is 1, 2 or 3, more preferably 2.

Preferably, e is 1, 2 or 3, more preferably 2.

Preferably, both h and e are 2.

When W³ or W⁴ is an alkyl group substituted with one or more groupsselected from —CO₂H, —SO₃H and —PO₃H₂, the alkyl group is preferably aC₁₋₆ alkyl group

Preferably, W³ and W⁴ are each independently —CO₂H, —PO₃H₂ or —SO₃H,more preferably, W³ and W⁴ are —SO₃H.

Preferably, one or both of the naphthyl groups present in the compoundof Formula (2) or a salt thereof are of Formula (2d):

wherein the asterisk (*) represents the point of attachment to therelevant azo groups in the compound of Formula (2).

Preferably, f is 0, 1 or 2, more preferably 0.

Preferably, g is 0, 1 or 2, more preferably 0.

Preferably, f and g are both 0.

S³ and S⁴ may each independently be any of the groups as previouslydescribed for S¹.

In a preferred compound of Formula (2) or a salt thereof:

-   each W₁ and W₂ independently is —CO₂H, —PO₃H₂ or —SO₃H;-   each S₃ and S₄ independently is C₁₋₄ alkyl or C₁₋₄ alkoxy;-   e and h each independently is 1, 2 or 3;-   f and g each independently is 0, 1 or 2.

Most preferably the compound of Formula (2) or a salt thereof is ofFormula (4) or a salt thereof:

The compound of Formula (4) is commercially available as C.I. DirectYellow 50.

The compound of Formula (2) or a salt thereof may be prepared by wellestablished diazotisation chemistry.

In a preferred synthetic route a substituted amino naphthylene isdiazotized and coupled to an optionally substituted aniline compound.The product of this diazotisation reaction is preferably coupledtogether using phosgene (COCl₂).

In the present invention the compounds of Formula (1) and Formula (2)may be in the form of the free acid (i.e. the protonated form) or in theform of a salt or a mixture thereof. Accordingly, any acidic groups suchas —CO₂H, —SO₃H and —PO₃H₂ present in the compounds of Formula (1) or(2) may be in the form of the free acid or a salt or a mixture thereof.

Preferably, the compounds of Formula (1) and Formula (2) are in the formof a salt.

Preferred salts are alkali metal salts, ammonium and substitutedammonium salts.

Preferred metal salts are the alkali metal salts, preferably lithium,sodium, potassium salts and especially sodium salts.

Preferred ammonium and substituted ammonium salts are ammonia, organicamines and quaternary organic amines (e.g. (CH₃)₄N⁺). The organic aminesmay be substituted with for example hydroxy groups (e.g. alkanolamines).

Preferably, the compound of Formula (1) or a salt thereof and of Formula(2) or a salt thereof are each independently in the form of a saltselected from the group consisting of metal, ammonium and substitutedammonium salts or a mixture thereof.

Preferably, the compounds of Formulae (1) and (2) are both in the formof the same salt.

The compounds of Formulae (1) and (2) in the form of the free acid maybe converted into salts using known techniques. For example, thecompound of Formula (1) in the form of the free acid may be neutralisedwith base such as an alkali metal hydroxide or an amine. Normally suchneutralisation is performed in an aqueous liquid medium.

The salt form can be exchanged by known techniques. For example, acompound of Formula (1) or (2) in the form of an alkali metal salt canbe converted into an ammonium salt by ultrafiltration with an ammoniasolution or by means of an ammonium ion-exchange resin.

Preferably, both of the compounds of Formulae (1) and (2) or saltsthereof are soluble in water. More preferably, both compounds aresoluble in water at a concentration of at least 5% by weight of thecompound.

Preferably, both of the compounds of Formulae (1) and (2) or saltsthereof are yellow, orange or brown in colour. More preferably, bothcompounds are yellow in colour when at a concentration of 5% by weightin water.

In a preferred composition, the compound of Formula (1) or a saltthereof and/or the compound of Formula (2) or a salt thereof arepurified by dialysis, reverse osmosis, ultrafiltration, ion exchange ora combination thereof. This purification may be before and/or after thepreparation of said composition.

The compound of Formula (1) or a salt thereof and the compound ofFormula (2) or a salt thereof may exist in tautomeric forms other thanthose shown in this specification. These tautomers are included withinthe scope of the present invention and its claims.

In a preferred embodiment the compound of Formula (1) or a salt thereofis of Formula (3) or a salt thereof and the compound of Formula (2) or asalt thereof is of Formula (4) or a salt thereof.

The compound of Formula (4) and salts thereof are known as C.I. DirectYellow 50.

Whilst the composition according to the first aspect of the presentinvention may comprise a compound of Formula (1) or salt thereof and acompound of Formula (2) or a salt thereof in any proportions relative toeach other we have found that certain weight ratios offer even moredesirable hue, ozone-fastness and light-fastness.

Preferably, the weight ratio of the compound of Formula (1) or a saltthereof to the compound of Formula (2) or a salt thereof is from 5:95 to95:5, more preferably from 50:50 to 95:5 and especially from 70:30 to90:10. Among other things, these ratios provide an excellent yellowshade for the yellow ink of a trichomatic (cyan, magenta and yellow)printing ink set.

The compositions according to the first aspect of the present inventionmay be prepared by simply adding a compound of Formula (1) or a saltthereof to a compound of Formula (2) or a salt thereof. More preferably,the two compounds are mixed so as to form a homogenous mixture. Themixing may be by dry blending using for example, a shaker mixer, rollermixer, tumbler mixer or the like. More preferably, mixing of thecompound of Formula (1) or a salt thereof and the compound of Formula(2) or a salt thereof is achieved by wet blending (i.e. mixing thecompounds together with a liquid). Preferably, the liquid is orcomprises water. It is especially preferable that both the compound ofFormula (1) and (2) are dissolved into a liquid medium, especially anaqueous liquid medium.

According to a second aspect of the present invention there is providedan ink comprising a composition according to the first aspect of thepresent invention and a medium.

In a preferred embodiment the ink comprises:

(a) from 0.01 to 30 parts of a composition according to the first aspectof the present invention; and

(b) from 70 to 99.99 parts of a medium;

wherein all parts are by weight and the number of parts of (a)+(b)=100.

The number of parts of component (a) is preferably from 0.1 to 20, morepreferably from 0.5 to 15, and especially from 1 to 5 parts. The numberof parts of component (b) is preferably from 99.9 to 80, more preferablyfrom 99.5 to 85, especially from 99 to 95 parts.

The medium may be a low melting point solid but is preferably a liquidmedium (preferably a liquid at 25° C.).

Preferably component (a) is completely dissolved in component (b).Preferably component (a) has a solubility in component (b) at 20° C. ofat least 5%, more preferably at least 10% by weight. This allows thepreparation of stable inks and concentrates which may be used to preparemore dilute inks and reduces the chance of the dye precipitating ifevaporation of the liquid medium occurs during storage.

In one embodiment the liquid medium is or comprises water (i.e. the inkis aqueous).

Preferred liquid media include water, a mixture of water and an organicsolvent and an organic solvent free from water.

When the liquid medium comprises a mixture of water and an organicsolvent, the weight ratio of water to organic solvent is preferably from99:1 to 1:99, more preferably from 99:1 to 50:50 and especially from95:5 to 80:20.

It is preferred that the organic solvent present in the mixture of waterand organic solvent is a water-miscible organic solvent or a mixture ofsuch solvents. Preferred water-miscible organic solvents includeC₁₋₆-alkanols, preferably methanol, ethanol, n-propanol, isopropanol,n-butanol, sec-butanol, tert-butanol, n-pentanol, cyclopentanol andcyclohexanol; linear amides, preferably dimethylformamide ordimethylacetamide; ketones and ketone-alcohols, preferably acetone,methyl ether ketone, cyclohexanone and diacetone alcohol; water-miscibleethers, preferably tetrahydrofuran and dioxane; diols, preferably diolshaving from 2 to 12 carbon atoms, for example pentane-1,5-diol, ethyleneglycol, propylene glycol, butylene glycol, pentylene glycol, hexyleneglycol and thiodiglycol and oligo- and poly-alkyleneglycols, preferablydiethylene glycol, triethylene glycol, polyethylene glycol andpolypropylene glycol; triols, preferably glycerol and 1,2,6-hexanetriol;mono-C₁₋₄-alkyl ethers of diols, preferably mono-C₁₋₄-alkyl ethers ofdiols having 2 to 12 carbon atoms, especially 2-methoxyethanol,2-(2-methoxyethoxy)ethanol, 2-(2-ethoxyethoxy)-ethanol,2-[2-(2-methoxyethoxy)ethoxy]ethanol,2-[2-(2-ethoxyethoxy)-ethoxy]-ethanol and ethyleneglycol monoallylether;cyclic amides, preferably 2-pyrrolidone, N-methyl-2-pyrrolidone,N-ethyl-2-pyrrolidone, caprolactam and 1,3-dimethylimidazolidone; cyclicesters, preferably caprolactone; sulphoxides, preferably dimethylsulphoxide and sulpholane. Preferably the liquid medium comprises waterand 2 or more, especially from 2 to 8, water-soluble organic solvents.

Examples of further suitable ink media comprising a mixture of water andone or more organic solvents are described in U.S. Pat. Nos. 4,963,189,4,703,113, 4,626,284 and EP 4,251,50A.

When the liquid medium comprises an organic solvent free from water,(i.e. less than 1% water by weight) the solvent preferably has a boilingpoint of from 30° to 200° C., more preferably of from 40° to 150° C.,especially from 50 to 125° C. The organic solvent may bewater-immiscible, water-miscible or a mixture of such solvents.Preferred water-miscible organic solvents are any of the hereinbeforedescribed water-miscible organic solvents and mixtures thereof.Preferred water-immiscible solvents include, for example, aliphatichydrocarbons; esters, preferably ethyl acetate; chlorinatedhydrocarbons, preferably CH₂Cl₂; and ethers, preferably diethyl ether;and mixtures thereof.

When the liquid medium comprises a water-immiscible organic solvent,preferably a polar solvent is included because this enhances solubilityof the dye in the liquid medium. Examples of polar solvents includeketones and alcohols (especially methyl ethyl ketone and C₁₋₄ alkanols).In view of the foregoing preferences it is especially preferred thatwhere the liquid medium is an organic solvent free from water itcomprises a ketone (especially methyl ethyl ketone) and/or an alcohol(especially a C₁₋₄-alkanol, more especially ethanol or propanol).

The organic solvent free from water may be a single organic solvent or amixture of two or more organic solvents. It is preferred that when themedium is an organic solvent free from water it is a mixture of 2 to 5different organic solvents. This allows a medium to be selected whichgives good control over the drying characteristics and storage stabilityof the ink.

When the liquid medium is an organic solvent free from water thecompounds of Formula (1) and (2) are preferably in the form of a saltwith a lipophilic amine. Preferred lipophilic amines contain at leastone C₄₋₂₀ alkyl group, more preferably at least one C₆₋₂₀ alkyl group.

Inks in which component (b) is an organic solvent free from water areparticularly useful where fast drying times are required andparticularly when printing onto hydrophobic and/or non-absorbentsubstrates, for example plastics, metal and glass.

Preferably, the low melting point solid is solid at 25° C. and melts ata temperature above 50° C. More preferably, the low melting point solidhas a melting point in the range from 60° C. to 125° C.

Suitable media which melt in this temperature range include long chainfatty acids, long chain sulfonamides or long chain alcohols, preferablythose having C₁₈₋₂₄ chains. The compound of Formula (1) or a saltthereof and the compound of Formula (2) or a salt thereof may bedissolved in the low melting point solid or they may be finely dispersedin it.

Inks according to the second aspect of the present invention may beprepared by adding together a compound of Formula (1) or a salt thereof,a compound of Formula (2) or a salt thereof and a medium.

Preferably, the medium is a liquid medium. When the liquid medium is orcomprises water, it is preferred that the water used to prepare the inkhas a relatively low conductivity.

Preferably, the water used to prepare the ink has a conductivity of lessthan 50 μS/cm, more preferably less than 10 μS/cm and especially lessthan 2 μS/cm. Water having these conductivity values can be prepared byknown methods such as deionization, reverse osmosis and distillation.

Preferably, the above components used to prepare the ink are mixedtogether so as to fully dissolve the compounds and to homogenize theink.

The inks according to the second aspect of the present invention mayalso contain additional components suitable for use in ink jet printinginks. Inks may contain for example viscosity and surface tensionmodifiers, corrosion inhibitors, biocides, kogation reducing additivesand surfactants.

Preferably, the ink has been filtered through a filter having a meanpore size of less than 10 μm, more preferably less than 5 μm, especiallyless than 2 μm, more especially less than 1 μm. In this way particulatematter is removed which could otherwise block the fine nozzles used inink jet printers.

Preferably, the ink has a viscosity of less than 50 mPa·s, morepreferably less than 20 mPa·s, especially less than 10 mPa·s at atemperature of 25° C.

Preferably, the ink has a concentration of halide ions of less than 500parts per million and more preferably less than 100 parts per million.It is especially preferred that the ink has less than 100, morepreferably less than 50 parts per million in total of divalent andtrivalent metals. Parts per million refer to parts by weight of therelevant ions or metals relative to the total weight of the ink. Anysuitable means to remove halide ions and/or di and trivalent metals maybe employed, e.g. ion exchange and ultra-filtration.

Preferably, the ink is aqueous and has a conductivity of less than 50μS/cm. Preferably, the conductivity of the ink is measured at atemperature of 25° C. Low conductivities are preferably achieved by, forexample, dialysis, ion exchange or ultra-filtration.

Preferably, the ink is yellow, more preferably the ink is yellow incolour when the total amount of the compound of Formula (1) or a saltthereof and the compound of Formula (2) or a salt thereof is 5% byweight relative to the ink.

According to a third aspect of the present invention there is provided aprocess for printing an image on a substrate comprising applying theretoan ink according to the second aspect of the present invention.

Preferably, the printing is performed by means of an ink jet printer.

The image may be in the form of a picture, text, graph, photograph orthe like without any particular limitation.

According to a fourth aspect of the present invention there is providedan ink jet printer cartridge comprising a chamber and an ink, whereinthe ink is present in the chamber and the ink is according to the secondaspect of the present invention.

According to a fifth aspect of the present invention there is provided asubstrate printed with an ink according to the second aspect of thepresent invention.

Preferred substrates include paper, transparent plastic or textilematerials.

Preferred substrates are those having a receptor layer for the ink. Thereceptor layer may be porous or non-porous.

According to a sixth aspect of the present invention there is providedthe use of a composition according to the first aspect of the presentinvention for preparing an ink jet printing ink comprising water andsaid composition, wherein the ink has a conductivity of less than 50μS/cm.

In the description of the present invention the words “a” or “an” arefrequently used to mean one or more where such meaning is appropriateand unless otherwise stated. Thus for example, “a compound of Formula(1) or a salt thereof” means one or more compound of Formula (1) orsalts thereof. For example, the composition according to the firstaspect of the present invention might comprise a compound of Formula (1)in the form of the free acid and the compound of Formula (1) in the formof a salt in combination with a compound of Formula (2) in the form of asalt. Similarly, a substrate means one or more substrates, a chambermeans one or more chambers and an image means one or more images.

The invention is further illustrated by the following Examples in whichall parts, percentages and ratios are by weight unless otherwise stated.

EXAMPLE 1

Dye (1)

Dye (1) was prepared and purified according to U.S. Pat. No. 6,488,752,column 10, line 1 to column 11, line 14. Dye (1) was compound of Formula(3), namely:

in the form of the sodium salt.Dye (2)

Dye (2) was obtained from Abbey Color Inc under the tradename ABCOL™Direct Yellow RLSW. Dye (2) was a compound of Formula (4), namely:

in the form of the sodium salt.

Compositions according to the present invention may be prepared bydissolving Dye (1) in the amounts indicated in Table 1, column 1 and Dye(2) in the amounts indicated in Table 1, column 2 in sufficientdeionized water to make the total composition up to 100 parts by weight.

TABLE 1 Ratio of amount Dye (1) parts Dye (2) parts Dye (1):Dye (2) 2 21:1 2 1 2:1 3.66 1 3.66:1   4 1 4:1 2 0.4 5:1 2 0.2 10:1 Ink Jet Printing Inks

The compositions described in Table 1 may be used to prepare ink jetprinting inks by adding one or more suitable additives. In particular,ink jet printing inks may be prepared containing 2-pyrrolidone (5parts), thiodiglycol (5 parts), Surfynol™ 465 (1 part from Air products)the amounts of Dyes (1) and (2) as indicated in Table 1 and deionizedwater so as to make the total up to 100 parts.

EXAMPLE 2 Further Inks

The further inks described in Tables I and II may be prepared whereinthe first column indicates the amount of Dye (1) in parts, the secondcolumn indicates the amount of Dye (2) in parts and the third columnindicates the ratio of the amounts of Dye (1) to Dye (2). All of thefurther inks in Tables I and II are made up to 100 parts with deionizedwater. The numbers quoted in the fourth column onwards refer to thenumber of parts of the relevant ingredient and all parts and ratios areby weight. The further inks may be applied to paper by thermal or piezoink jet printing.

The following abbreviations are used in Tables I and II:

PG=propylene glycol

DEG=diethylene glycol

NMP=N-methyl pyrollidone

DMK=dimethylketone

IPA=isopropanol

MeOH=methanol

2P=2-pyrollidone

MIBK=methylisobutyl ketone

P12=propane-1,2-diol

BDL=butane-2,3-diol

CET=cetyl ammonium bromide

PHO=Na₂HPO₄ and

TBT=tertiary butanol

TDG=urea

TABLE I Dye Dye Ratio of Na (1) (2) Dye (1):Dye (2) PG DEG NMP DMK NaOHStearate IPA MEOH 2P MIBK 5 0.5 10:1  5 6 4 5 4 0.5 8:1 5 5 0.2 3 1 3:13 3 3 5 1 2 2 1:1 8 1 6 3 2:1 5 0.2 4 5 4 1 4:1 9 0.5 0.5 9 4.7 1.33.6:1   4 15 3 3 6 10 5 4 3.7 2.3 1.6:1   20 10 4.2 1.8 2.3:1   5 4 5 65 4 2 2:1 3 5 2 10 0.3 3 3 1:1 5 4 6 5 4 6 5 2 0.5 4:1 4 1.67 0.83 2:1 55 1.87 0.63 3:1 2 6 2 5 1 4 2.08 0.42 5:1 5 15 2.25 0.25 9:1 11 5 2.30.2 11.5:1   2 10 2 6 1.25 1.25 1:1 7 0.3 3 2 0.5 4:1 2 20 2 1 3 3 2.080.42 5:1 4 5

TABLE II Dye Dye Ratio of (1) (2) Dye (1):Dye (2) PG DEG NMP CET TBT TDGBDL PHO 2P PI2 5 0.5 10:1  15 0.2 5 4 0.5 8:1 5 1.2 5 3 1 3:1 5 5 0.155.0 0.2 2 2 1:1 6 4 0.12 6 3 2:1 4 8 0.3 6 4 1 4:1 10 5 0.2 4.7 1.33.6:1   5 5 0.3 3.7 2.3 1.6:1   10 4 1 4 11 4.2 1.8 2.3:1   4 10 3 2 6 42 2:1 6 3 3 3 1:1 9 7 3.0 0.95 5 2 0.5 4:1 5 11 6 1.67 0.83 2:1 7 7 1.870.63 3:1 5 5 5 0.1 0.2 0.1 5 0.1 5 2.08 0.42 5:1 10 2.25 0.25 9:1 10 2.30.2 11.5:1   5 12 5 1.25 1.25 1:1 2 8 15 5 2 0.5 4:1 8 12 2.08 0.42 5:110

1. A composition comprising a compound of Formula (1) or a salt thereofand compound of Formula (2) or a salt thereof:

wherein: A is an aryl or heteroaryl group; Q¹ and Q² each independentlyis an optionally substituted phenylene group; R¹, R², R^(a) and R^(b)each independently is H, optionally substituted alkyl, optionallysubstituted aryl or optionally substituted arylalkyl; each W¹, W², W³and W⁴ independently is a —CO₂H, —SO₃H, —PO₃H₂ group or an alkysubstituted with one or more groups selected from the group consistingof —CO₂H, —SO₃H, and —PO₃H₂; each S¹, S², S³ and S⁴ independently is asubstituent other than those defined for W¹, W², W³ and W⁴; a and d eachindependently is from 1 to 5; b and c each independently is from 0 to 4;(a+b) has a value of from 1 to 5; (c+d) has a value of from 1 to 5; eand h each independently is from 1 to 7; f and g each independently isfrom 0 to 6; (e+f) has a value of from 1 to 7; and (g+h) has a value offrom 1 to
 7. 2. A composition according to claim 1 wherein in thecompound of Formula (1) or a salt thereof: each W¹ and W² independentlyis —CO₂H, —SO₃H or a C₁₋₆ alkyl substituted by —CO₂H or —SO₃H; each S¹and S² independently is C₁₋₆ alkyl, phenyl, nitro, halo, cyano, —CF₃,—NH₂, C₁₋₆ alkoxy, —SC₁₋₆ alkyl, —C₁₋₆ alkyl substituted by —OH or—NHC(O)C₁₋₆ alkyl; R¹ is H or C₁₋₆-alkyl optionally substituted by —OH,—SO₃H or —CO₂H; R² is C₁₋₄ alkyl; a and d each independently is 1 or 2;b and c each independently is 0, 1 or 2; and in the compound of Formula(2) or a salt thereof: each W₁ and W₂ independently is —CO₂H, —PO₃H₂ or—SO₃H; each S₃ and S₄ independently is C₁₋₄ alkyl or C₁₋₄ alkoxy; e andh each independently is 1, 2 or 3; f and g each independently is 0, 1 or2.
 3. A composition according to claim 1 wherein the compound of Formula(1) or a salt thereof is of Formula (3) or a salt thereof and thecompound of Formula (2) or a salt thereof is of Formula (4) or a saltthereof:


4. A composition according claim 1 wherein the weight ratio of thecompound of Formula (1) or a salt thereof to the compound of Formula (2)or a salt thereof is from 50:50 to 95:5.
 5. A composition according toclaim 1 wherein the weight ratio of the compound of Formula (1) or asalt thereof to the compound of Formula (2) or a salt thereof is from70:30 to 90:10.
 6. A composition according to claim 1 wherein thecompound of Formula (1) or a salt thereof and of Formula (2) or a saltthereof is in the form of a salt selected from the group consisting ofmetal, ammonium and substituted ammonium salts or a mixture thereof. 7.A composition according to claim 1 wherein the compound of Formula (1)or a salt thereof and/or a compound of Formula (2) or a salt thereof arepurified by dialysis, reverse osmosis, ultrafiltration, ion exchange ora combination thereof, before and/or after preparation of saidcomposition.
 8. An ink comprising a composition according to claim 1 anda medium.
 9. An ink according to claim 8 comprising: (a) from 0.01 to 30parts of the composition according to any one of claims 1 to 8; and (b)from 70 to 99.99 parts of a medium; wherein all parts are by weight andthe sum of the parts (a)+(b)=100.
 10. An ink according to claim 9wherein the medium is a liquid medium.
 11. An ink according to claim 10wherein the liquid medium is or comprises water and the water used toprepare the ink has a conductivity of less than 50 μS/cm.
 12. An inkaccording to claim 10 having a viscosity of less than 50 mPa·s at atemperature of 25° C.
 13. A process for ink jet printing an image on asubstrate comprising applying thereto an ink according to claim
 8. 14.An ink jet printer cartridge comprising a chamber and an ink, whereinthe ink is present in the chamber and the ink is according to claim 8.15. A substrate printed with an ink according to claim 8.